ENCRYPTION METHOD 4- PERMUTATION CIPHER

 

* In this encryption, only the places of the letters are changed.

* Curriculum topics related to Permutation Cipher:/Aim Permutation function, matrix

EXAMPLE

ENCRYPTION

If you want to encrypt  plaintext "COME TO THE USUAL PLACE TONIGHT"

 with  (12345-43125) permütation and "CLASS" key.

Firsly you will divide the plaintext into pieces the length of the key. Our key "CLASS" have 5 letter so it's lenght 5. You will divide the plain text into five letter parts.(The keyword only tells us to divide the plain text into groups of how many letters).

COMET OTHEU SUALP LACET ONIGH  Txxxx  (Instead of missing letters, x is written) 

You have split the plain text into six parts. So you'll need six row.The number of columns should be 5 as the length of the key. Then you will write the given permutation first line, and the parts of the plaintext on the other lines in order. 

4	3	1	2	5
C	O	M	E	T
O	T	H	E	U
S	U	A	L	P
L	A	C	E	T
O	N	I	G	H
T	x	x	x	x

You will then rewrite each row in the order that the permutation indicates.You will find ciphertext "MEOCTHETOUALUSPCEALTIGNOHxxxTx"

Method:Permutation, Key= CLASS,Permutation=(12345- 43125),

Plaintext=COME TO THE USUAL PLACE TONIGHT, Ciphertext= MEOCTHETOUALU SPCEALTIGNOHxxxTx

 

DECRYPTION

 If you want to decrypt  cipher text "MEOCTHETOUALUSPCEALTIGNOHxxxTx"

 with  (12345-43125) permütation and "CLASS" key.

 You have to look from invers to permutation. So, you will use inverse permutation (12345-34215) permutation.The other steps are similar to encryption. You will divide the cipher text into the length of the key.

MEOCT HETOU ALUSP CEALT IGNOH xxxTx

3	4	2	1	5
M	E	O	C	T
H	E	T	O	U
A	L	U	S	P
C	E	A	L	T
I	G	N	O	H
x	x	x	T	x

You will then rewrite each row in the order that the permutation indicates.You will find ciphertext "COMETOTHEUSUALPLACETONIGHTxxxx"  

We used x's to fill blanks, they are unnecessary. Separating words is up to you in this encryption:)

Finally we achieve "COME TO THE USUAL PLACE TONIGHT"